<template>
  <ul class="list">
    <li class="item"
        v-for="item in letters"
        :key="item"
        :ref="item"
        @click="handleClick"
        @touchstart.prevent="handleTouchStart"
        @touchmove="handleToucheMove"
        @toucheend="handleTouchEnd">
      {{item}}
    </li>
  </ul>
</template>

<script>
  export default {
    name: 'Alphabet',
    props: {
      cities: Object
    },
    data(){
      return{
        touchStatus: false,
        startY: 0,
        timer: null
      }
    },
    updated(){
      this.startY = this.$refs['A'][0].offsetTop;
    },
    methods: {
      handleClick(e){
        // console.log(e.target.innerText)
        this.$emit('change', e.target.innerText)
      },
      handleTouchStart(){
        this.touchStatus = true
      },
      handleToucheMove(e){
        if(this.touchStatus){
          if(this.timer){
            clearTimeout(this.timer)
          }
          this.timer = setTimeout(() => {
            const touchY = e.touches[0].clientY - 79;
            const index = Math.floor((touchY - this.startY) / 20)
            if(index >= 0 && index < this.letters.length){
              this.$emit('change', this.letters[index]);
            }
          },16)
        }
      },
      handleTouchEnd(){
        this.touchStatus = false
      }
    },
    computed: {
      letters(){
        const letters = [];
        for (let i in this.cities){
          letters.push(i);
        }
        return letters
      }
    }
  }
</script>

<style scoped lang="stylus">
  @import "~style/varibles.styl"
.list{
  display flex
  flex-direction column
  justify-content center
  position absolute
  right 0
  top 1.58rem
  bottom 0
  width .4rem
}
  .item{
    text-align center
    line-height .4rem
    color $bgColor
  }
</style>
